Boron hydride salts, in particular the nonmetal salts of decahydrodecaboric acid, had been discovered to have particular utility in the field of high energy fuels. They may be used as constituents of pyrotechnic compositions and in propellants. For example, non-metallic salts of the decahydrodecaborate ion, and exemplary uses, are disclosed in the co-pending applications of common assignment entitled "Ignition and Pyrotechnic Compositions," Ser. No. 694,625, filed June 10, 1976 and "Coprecipitated Pyrotechnic Composition Processes and Resultant Products," Ser. No. 694,626, filed June 10, 1976.
The present invention teaches a new non-metal salt of decahydrodecaboric acid, which exhibits stable physical properties, and is of itself a high energy monopropellant. The compound is very unusual in that it contains only boron, nitrogen, carbon, and hydrogen, but no oxygen.
A particular objective in preparing compounds suitable for certain types of pyrotechnic usage is to achieve a high gas output and low molecular weight combustion products, when the compound is burned. Combustion products such as hydrogen (H.sub.2) and nitrogen (N.sub.2) gas fulfill this requirement. In preparing salts useful as pyrotechnic fuels from an anion such as decahydrodecaborate (-2)(B.sub.10 H.sub.10 -2), it has been found advantageous to use a cation containing a high weight fraction of atomic nitrogen and hydrogen. The triaminoguanidinium ion, chemical formula C(NHNH.sub.2).sub.3.sup.+1 has been found to be such a cation. In addition, the corresponding Br.PHI.nsted base of the ion, free triaminoguanidine, is a strong base, which imparts to the cation, and thus the salt, a high degree of chemical stability.
Other decahydrodecaborate (-2) salts employing guanidine chemistry have been previously investigated by the present inventor. The simple guanidine salt is disclosed in my earlier application "Bis-Guanidinium Decahydrodecaborate and a Process of Its Preparation," Ser. No. 694,627, filed June 10, 1976, which is now U.S. Pat. No. 4,002,681. This simple salt was found to be useful as a high energy pyrotechnic fuel, and was by itself thermochemically stable; i.e., has a substantial negative heat of formation as commonly defined by those practiced in the art. The compound which is the subject of the present invention, by contrast, combusts by itself releasing internal energy, without need of an additional oxidizing material, which suggests the presently taught compound has a substantial positive heat of formation. As a result, the compound taught herein is useful as a monopropellant in its own right, or alternatively, can be used with additional oxidizer to modify its combustion properties. Specifically, such inorganic oxidizing agents as potassium nitrate, quanidine nitrate and ammonium percholorate may advantageously be employed, in concentrations from 0-90%, by weight.